For mobile electronic equipment including a mobile phone, a notebook size computer, a mobile cassette player, compact disc (CD) player, and mini disc (MD) player, drop-down is an ever-present accident when considering its intended use. Accordingly, protecting the equipment from impact caused by the drop-down has now been a growing need. A typical failure comes from distortion of a motherboard mounted on the equipment due to drop-down impact, by which some on-board components have shorts in the wiring, or come off the board. Therefore, to protect the equipment from such accidents, following steps should be taken: i) selecting a material and a structure of electronic equipment to be tested; ii) determining a drop-down height and direction; iii) simulating drop-down impact acceleration applied to each section of the equipment; and then iv) getting feedback from the result and improving the design of the inner structure, for example, the position and method of installing a circuit board. However, the drop-down impact acceleration during falling greatly varies between falling objects, and the acceleration applied to an object has significant magnitude. Furthermore, resonance frequency caused by drop impact greatly depends on the structure of an object. The reasons above have been obstacles to detection of drop-down impact acceleration applied to a falling object.